Theres alot of personal preference with golf balls. Each of the major ball companies offer a decent ball which dosnt cost £40 a dozen. For example Titleist do the NXT & NXT Tour (they are just launching a new range I believe) Wilson do the DX2 & DX3 and Srixon do some good stuff as well.
You would probably want a distance based ball as per the suggestions above.
Just forget the crap about Pro V1s being the ball to play. I prefer Callaway IS as they feel less spinny to me, but they can lack a bit on the durability side.
PS _ If you havent already do pop into the Lounge and introduce yourself.
1) How well you hit the ball, and
2) How it feels to you.
1) If you are getting a proper ball/turf descending blow creating backspin type strike, then an Ad333 type ball is worth considering. But if you are just as likely to thin it/fat it/cut it open as hit a great one, then stick with as durable a bit of kit as you can find - eg TopFlite XL or similar.
2) It doesn't matter how well you hit a ball getting to the green, once you are there everyone, no matter what handicap, can feel the difference when you hit a ball with a putter. Try a few different types and see which one comes off the putter face best for you. The harder balls tend to come off a little faster, so you might find it harder to judge pace.
Whichever ball you decide on, try to stick with it, and not use too many different types, so you can judge how your game is improving over time.
I've tried most balls on the market and the best ball in terms of feel and performance when looking at value for money is in my opinion the Pinnacle Precision. I find this ball very similar to the Srixon AD333 which has lots of fans however at around £10 for 15 balls it's a no brainer.
All depends on your budget. For upto £20 a dozen I like Bridgestone e6, Srixon AD333 and Wilson Staff Dx2. Cheaper good options are Pinnacle Precisions and Noodles.